1. Field of the Invention
This invention relates to an ink jet print head and an ink jet printer, and more particularly to an ink jet print head in which the volume of an individual ink channel filled with ink is changed by a piezoelectric actuator to jet ink to a recording paper from the ink channel to make a desired print. The invention additionally relates to an ink jet printer, for a word processor, a facsimile machine, a plotter or the like, in which such a print head is mounted.
2. Description of the Related Art
As a printer for a word processor, a facsimile machine or a plotter, various types of ink jet printers have currently been put to practical use in which a piezoelectric actuator is used.
One of these conventional ink jet printers is a so-called Kyser type, which is disclosed in, for example, U.S. Pat. Nos. 4,189,734 and 4,216,483. Generally this Kyser type print head has the following construction. There are supported on a print head base individual ink channels branching from a common ink channel and leading to respective jet nozzles. A diaphragm array is attached to the head base so as to cover the individual ink channels; when the flexure of the diaphragm is vibrated, the volume of the individual ink channel is varied to make an ink jet to the paper at every vibration. For driving the diaphragm to vibrate, piezoelectric devices are fixed to the diaphragm array at positions corresponding to the individual ink channels; upon application of a voltage to the selected piezoelectric devices, they will be displaced to move the diaphragm array locally. As a result, the individual ink channels corresponding to the moved portion of the diaphragm array will change in volume to thrust out ink from the nozzles.
Various improvements have been made to this Kyser type ink jet printer, as disclosed in Japanese Patent Laid-Open Publications Nos. SHO 63-252750 and SHO 63-247051 and U.S. Pat. Nos. 4,879,568, 4,887,100, 4,992,808, 5,003,679 and 5,028,936 corresponding to the last-named Japanese Publication.
With this improved print head, it is possible to provide a high-density ink jet printer which is operable by less energy.
However, modern ink jet printers require much higher dot density, and yet the piezoelectric multi-channel diaphragm array can not cope with such high-density printing. Thus the conventional arrangement would cause only a low printing quality with an attempted increase in print dot density, and so it is impossible to satisfy the demands for high density and high quality at the same time. If attempts were made to achieve high-density and high-quality printing by a mass-production print head, the cost of production would have exceeded the practical range.
High-quality and high-density printing also needs high-viscosity ink. When using high-viscosity ink, it is necessary to shorten the individual ink channel of the print head to reduce fluid friction. With the conventional print head, it is difficult to shorten the individual ink channels, and so high-viscosity ink cannot be used, or it will cause jamming. In other words, with the conventional arrangement, the extent to which the diaphragm is to be vibrated by the driving force of the piezoelectric devices is limited, otherwise the foregoing problems occurred. It is also difficult to achieve a multi-channel print head which is high in both density and quality and is small in size.
Therefore a printer equipped with such an ink jet print head is large in size.
Further, since the extent of vibration of the diaphragm is small, the individual ink channel would necessarily be long, which makes the printer large in size and occasionally causes jamming. Particularly if high-viscosity ink is used in an attempt to achieve high-speed and high-density printing, it would very probably result in jamming so that various reconstructions would be necessary, thus making the printer much larger in size.